| Summary: | The aerosol–cloud interactions due to black carbon (BC) aerosols, as well as the implied climate responses, are examined using an aerosol module in the coupled atmosphere–ocean general circulation model MPI-ESM. BC is simulated to enhance cloud droplet number concentration (CDNC) by 10–15% in the BC emission source regions, especially in the Tropics and mid-latitudes. Higher CDNC and reduced auto-conversion from cloud water to rain water explains the increased cloud water path over the tropical regions (30$ ^\circ $S–30$ ^\circ $N) in the model. In the global mean, the cloud water– as well as precipitation changes are negligibly small. The global-mean effective radiative forcing due to aerosol–cloud interactions for BC is estimated at $ -0.13\,\pm \,0.1\,\text{ W}\,\mathrm{m}^{-2} $, which is attributable to the increase in CDNC burden and (regionally) cloud water in the model. Global mean temperature and rainfall response were found to be $ -0.16\,\pm \,0.04\,\text{ K} $ and $ -0.004\, \pm \, 0.004\,\text{ mm}\,\mathrm{day}^{-1} $, respectively, with significantly larger regional changes mainly in the downwind regions from BC sources.
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